2013-02-07 VIR Measles, Mumps and Slow Viruses Flashcards
Describe the structure of measles and mumps
both measles and mumps are paramyxoviruses:
Has a single piece(-)ssRNA (therefore virion has a viral RDRP and cannot undergo rapid and major antigenic shifts) in helical nucleocapsid with an envelope embedded with H
Compare the antigenic relationship of measles and mumps to other classic paramyxoviruses
mumps has a antigenically related to the parainfuenza viruses but measlues isn’t
How is mumps spread?
respiratory droplets
How is measles spread?
respiratory droplets
Comare the infection location, incubation time and immunity length for measles/mumps vs. influenza/parainfluenza
parainflu and flu are local (i.e. non-systemic) infections vs. obligatory viremia in measles and mumps
this means longer incubation time for measles/mumps
and that measles/mumps gives longer (i.e. lifelong immunity)
What causes so-called “slow” infections?
1) conventional viruses w/ delayed onset of sx
2) unconventional agents (e.g. prions)
Describe the course of a slow viral infection.
Takes years for sx to set in
slow but relentless course to death
What are prions?
Infectious proteins that lack any detectable nucleic acid
What are prion diseases called, as a class, in humans?
Give us the list of them all.
spongiform encephalopathies
Creutzfel-Jacob Disease (CJD), Variant Creutzfeld-Jacob (vCJD), Kuru, Gerstmann-Straussler-Scheinker Syndrome (GSS) and Fatal Familial Insomnia
What is the source of variation in paramyxoviruses? How much does it ∆ w/ time?
unsegmented RNA genomes so no reassortment; only source is mutation though this does happen faster b/c RNA pol doesn’t proof
Therefore paramyxoviruses like measles and mumps are antigenically quite stable (i.e. they don’t change much and the original vaccines we have for them still work)
Define pantropic
Measles is considered a “pantropic” infection because it affects nearly all parts of the body
Mumps
Family = ?
Epidem = ?
Trans = ?
Incubation = ?
Pathogen w/ s/sx = ?
Dx = ?
Prevention = ?
Tx = ?
Family = paramyxoviridae
Epidem = worldwide, peaks in winter; some reccent epidemics have occured in North America
Trans = saliva—>resp droplets
Incubation = ~3 wks
Pathogenesis, s, sx = virus grows in resp epithel—>local lymph nodes—>viremia—>parotids etc.
most people are symptomic (70%)
prodrome: 1st malaise, anorexia, fever; 2nd uni- or bi-lateral parotiditis—>spreads via saliva; 3rd other encapsulated organs via viremia (e.g. testes = orchitis in 30% of post-pubertal males; meninges causing aseptic meningitis pretty common; ovaries and pancrease less common)
Dx = usu clinical; viral culture from saliva, CSF or urine; PCR also; 4x incr in IgG
Prevention = live attenuated vaccine given twice in childhood
Tx = none
Measles
Family = ?
Epidem = ?
Trans = ?
Incubation = ?
Pathogen w/ s/sx = ?
Dx = ?
Prevention = ?
Tx = ?
Family = paramyxovirus
Epidem = highly infectious! humans = sole carriers; most contagious dz known but always antigenically the same! caused dz q3 years (# non-immune incr w/ births breakdown in herd immunity)
Trans = resp drops and also tears and urine
Incubation = 2 weeks from exposure to rash
Pathogen w/ s/sx = resp to resp; growth in epithel, lymph nodes and conjunctiva; 100% attack rate (everyone exposed gets it); 1st) prodrome w/ coryza; 2) koplik’s spots (see photo); 3) pathognomonic maulopapular erythema that starts on head and spreads inferiorly
—causes syncytia; rare giant-cell pneumonia w/o rash chez les personnes sans cell-mediated immunity; show cell-med imm imprt for rash
—suppressed cell-mediated immunity—>2° infections that cane be deadly esp. in resource-limited situations = ANERGY
—Photophobia also common
—1:20 pneumonia; 2° bact. otitis media; acute encephalitis —> neuro def if survived
—1-3:1000 death rate
Dx = usu. clinically; culture, 4x incr [Ab] or PCR also available
Prevention = live, attenuated vaccine
Tx = no antiviral therapy available
Progressive Multifocal Leukoencephalopathy (PML)
Family = ?
Epidem = ?
Trans = ?
Incubation = ?
Pathogen w/ s/sx = ?
Dx = ?
Prevention = ?
Tx = ?
WILL BE ON BOARDS
Family = polyomaviridae—>JC virus
Epidem = most common chez les immunodéprimées
Trans = unbiquitous
Incubation = long long time
Pathogen w/ s/sx = immunocompromizaiton causes affects oligodendrocytes causing demyelenation: visual field defects, mental status ∆s, weakness—>blindness, dementia, coma and death =(
Dx = PCR of brain biopsy or CSF
Prevention = don’t get cancer or HIV?
Tx = cidofovir may help, but really no effective tx
Subacute Sclerosing Panencephalitis (SSPE)
Family = ?
Epidem = ?
Trans = ?
Incubation = ?
Pathogen w/ s/sx = ?
Dx = ?
Prevention = ?
Tx = ?
Family = Paramyxoviridae—>MEASLES VIRUS
Epidem = kids several years after initial infection
Trans = ?
Incubation = “long incubation time”
Pathogen w/ s/sx = slow cognitive decline, psych disturbances—remissions—>terminal paralysis and blindness
Dx = titer of blood and CSF: VERY HIGH Ig titers; Measles Ag in CSF
Prevention = vaccination? still 1:1,000,000 risk of SSPE w/ vaccination as compared to 1:100,000 w/ actual dz
Tx = none =(
Scrapie
Family = ?
Epidem = ?
Trans = ?
Incubation = ?
Pathogen w/ s/sx = ?
Prevention = ?
Sheep prion dz
genetic predisposition (inbred sheep at increased risk)
sheep goes crazy scrapes off all its skin
cannot be prevented with UV sterilzation, alyklating agents or formaldehyde
Kuru
Family = ?
Epidem = ?
Trans = ?
Pathogen w/ s/sx = ?
Family = prion dz
epidem = limited to Foré
Trans = ingestion, direct injection into brain of chimps, possibly via open skin?
Pathogen = Kuru is a progressive degenerative disorder of the CNS, especially the cerebellum; similar to Scrapie
CJD
Family = ?
Epidem = ?
Trans = ?
Incubation = ?
Pathogen w/ s/sx = ?
Dx = ?
Prevention = ?
Tx = ?
Creutzfeld Jacob Disease
Family = prion dzs
Epidem = most cases in 50-70 y/o’s
Trans = 1) sporadic = most cases (sCJD); 2) genetic predisposition (fCJD familial); 3) iatrgoenic (iCJD) **Not linked to diet—vegetarians and meat-eaters have similar incidence
Incubation = clinically with: brain biopsy showing SE; imaging and EEG; definitely with: antiprion Abs
Pathogen w/ s/sx = dementia w/ behav ∆s/mem loss/confusion and myoclonic jerking
Dx = ?
Prevention = no vaccine
Tx = no tx
Variant CJD
- A spongiform encephalopathy of cows (“mad cow disease”) reached epidemic status in Great Britain as a result of using brains and bone marrow from cows and sheep in the manufacture of bovine food.
- An outbreak of “atypical human Creuzfeld-Jacob disease” (vCJD) in Great Britain has been linked epidemiologically to eating beef from infected cows. Cows were infected by being fed dead cow brains in their feed. =/
Paramyxoviruses
Nucleic acid set-up?
Virion structure?
How does it multiply?
Examples?
NA = single (-)ssRNA
Virion = helical enveloped
REPLICAITON:
1) also uses hemagglutinin to adsorb to cell
2) have only one RNA segment (therefore no antigenic shift) and replicates genome in cytosol, but otherwise similar to influenza/orthomyxoviridae: Virion contains RNA-dependent RNA pol, budding, etc.
EXAMPLES: parainfluenza (Croup), RSV, Measles, mumps
Polyomaviridae (Formerly Papovavirus)
Nucleic acid set-up?
Virion structure?
(How does it multiply?)
Examples?
Nucleic acid set-up? circular dsDNA genome
Virion structure? non-enveloped
(How does it multiply?)
Examples? JC virus, BK virus and SV40 virus
What is the most common cause of croup?
parainfluenza infection (~75% of cases)
